It has long been a desire to increase the operating performance of internal combustion engines. Electronic engine controls have been created with this goal in mind. For example, it is now common for an engine to include at least one oxygen sensor which provides data to an engine control, the control utilizing the data to optimize the air to fuel ratio by changing the fuel injection timing or volume.
As the cost of fuel increases, it has also become extremely important to improve the operating performance of internal combustion engines in order to reduce their fuel consumption rate. In addition, engines must run efficiently in order that the exhaust produced falls within environmental law parameters.
A variety of operating parameters affect the engine operating condition. For example, the incoming air temperature and pressure is related to the air to fuel ratio. Thus, it is known to measure the air temperature and pressure and then compensate for variations in air density when calculating the desired fuel delivery rate, as with an engine control similar to that described above.
In the field of marine power, one operating parameter which greatly affects engine performance is exhaust back pressure. It is common for the exhaust outlet of the engine to be positioned within a body of water of the watercraft which the engine is powering. The water pressure creates a resistance to the flow of exhaust through the engine, thus causing exhaust back pressure.
The back pressure changes the amount of air and fuel which may enter the combustion chamber from that which would normally enter at a given throttle and injection setting, causing a variance in the air/fuel ratio from a desired ratio. The variation in the air/fuel ratio may result in engine stalling, increased emissions, low power output and other problems.
It is, therefore, an object of the present invention to provide an engine control for controlling the operating condition of an engine dependent upon an operating condition affecting exhaust back pressure within the exhaust system of the engine.